| Material like oil and natural gas is transport through the pipeline with pressure inthe oil industry, so the natural gas gathering and transportation system are equipped withbooster stations. A ancillary pressure vessel is usually welded to the output ofcompressors or the sink department of pipeline to reduce the impact of pulsatingpressure to pipeline followed up, which is generated when compressors work. Pressurevessel works under the condition of uneven force, thus it is prone to crack defects. If thecrack is not detected effectively, spill accident is to be happened, which will affectsproduction safety seriously.In the domestic, traditional non-destructive testing methods(NDT) such asultrasonic, magnetic particle, penetrant testing and so on are applied to detect fillet weldcracks in pressure vessels. However, there are some defects undetected in actual fieldtesting sometimes due to particularity of fillet weld and limitation of traditional NDTmethods, which lead to the accident of leak finally. So it is most significant to proposean efficient NDT program for the detection of fillet weld cracks in pressure vessels.At first, the form and characteristics of the fillet weld crack in the pressure vesselare analyzed. A series of reason for cracks are summarized according to comprehendingthe detected object and the working conditions. A NDT program based on ultrasonicphased array technology is developed according to actual detection requirements andreference to domestic and international NDT technology.Parameters applied in the detection process are confirmed by analyzing thestructural characteristics of fillet weld. Structural size of the array probe is designed. Apre-processing analog circuit for detection signal is built. The function of time-delay isrealized applying to the FPGA technology, which is an important function for thecontrolling of ultrasonic phased array testing and ensures the realization of ultrasonicphased array electronic focus function. The developing platform of LabVIEW is appliedto design analysis software on host computer of the detection system. The analysissoftware is used to the processing and display of the detection information receivedfrom receiver module.In the design of detection signal transceiver module, function of nanosecond timedelay is completed with the application of a relatively simply reliable algorithmImplemented on FPGA hardware, which meets the requirements of ultrasonic phasedarray inspection for the delay time controlling; In the design of host computer analysismodule, method of useful information screening based on the detection characteristicsof the echo signal is used to Simplify the subsequent processing module; Algorithm of“smooth wave by minimum elimination†is designed in an innovative way, which improves the accuracy of the ultrasonic phased array inspection system by effectivelyfiltering out the noise impact and highlighting characteristics of the echo signal. |
